Temporarily reducing the diametrical opening of apertures by use of a removable annular member

ABSTRACT

A method for temporarily reducing the diametrical opening of the apertures in a shadow mask by placing annular rings in the opening of the apertures to partially reduce the effective opening of the apertures in the mask without altering the physical characteristics of the mask.

United States Patent Mears et al.

[ 1 Mar. 14, 1972 [54] TEMPORARILY REDUCING THE DIAMETRICAL OPENING OF APERTURES BY USE OF A REMOVABLE ANNULAR MEMBER [72] lnventors: Norman B. Mears, St. Paul; John J. Frantzen, North St. Paul, both of Minn.

[73] Assignee: Buckbee-Mears Company, St. Paul, Minn.

[22] Filed: Feb. 9, 1970 [21] App]. No.: 9,639

[52] US. Cl ..95/1 [Sl] Int. Cl. ..G03h 27/02 [58] Field of Search ..95/1, 85

Primary Examiner.lohn M. Horan Attorney-Stryker and Jacobson 57 ABSTRACT A method for temporarily reducing the diametrical opening of the apertures in a shadow mask by placing annular rings in the opening of the apertures to partially reduce the effective opening of the apertures in the mask without altering the physical characteristics of the mask.

7 Claims, 9 Drawing Figures ill IIIIHIII Il ||u| lllln llllllllll lmllll l LIGHT SOURCE Patented March 14, 1972 2 Sheets-Sheet 1 20b Fig, 2 Fig 3 SHAKER MECHANISM VACUUM PUMP INVENTORS NORMA/V B. MEARS JOHN J. FRANTZE/V ATTORNEYS Patented March 14, 1972' NORMA/V B. MEARS JOHN .1. FRANTZE/V BY w wm ATTORNEYS 'IEMPORARILY REDUCING THE DIAMETRICAL OPENING OF APERTURES BY USE OF A REMOVABLE ANNULAR MEMBER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to fabrication or assembly of color TV picture tubes containing aperture masks and, more particularly, to the manufacturing steps utilizing the aperture mask to form a phosphorus dot pattern on the face plate of the TV picture tube.

2. Description of the Prior Art Conventionally, the three primary color phosphorus dots are formed on the inside surface of the glass face plate of color TV picture tubes by using an aperture mask as a pattern. After the phosphorus dots have been formed, the same mask is permanently attached in the tube to provide its normal function in directing electron beams to strike the proper phosphorus dots. Generally, after forming the phosphorus dot pattern by using the mask as a pattern, the apertures in the mask are enlarged before permanently attaching the mask to the TV picture tube. The purpose of having the permanently attached aperture mask with larger openings than the mask when it is used as a pattern is to produce a brighter picture. In order to have the same holes two different diameters at two different times requires either enlarging the openings after using the mask as a pattern or temporarily stepping down the diameter of the openings prior to forming the phosphorous dot pattern on the face plate.

Conventionally, various processes have been used for forming the three primary colored phosphorus dots in the viewing face of the tube. The construction, operation and function of these aperture masks are all disclosed and described in the prior art, for example, in an article titled Constructing the Tri-colored Picture Tube Electronics, pg. 86, published May 1951; U.S. Pat. No. 3,l46,368 to Fiore et al., U.S. Pat. No. 2,795,719 to Morrell; U.S. Pat. No. 2,802,964 to Jeste and U.S. Pat. No. 3,23 l ,380 to Law. The Law patent relates to the temporarily stepping down of the apertures while the rest of the patents apertures to the process of constructing, operating, and functioning of the aperture mask.

Of the prior art methods, numerous processes have been employed which, in one way or another alter the physical characteristics of the mask sometime during the processing or laying the phosphorus dot pattern on the face plate. For example, one process involves etching the openings in the mask larger after laying the phosphorus dot pattern. Another process involves etching the holes to the largest diameter, and then electroplating material into the holes to reduce the diameter of the holes in order to lay the phosphorus dot pattern. After laying the phosphorous dot pattern the electroplated material is etched away thus returning the openings of the mask to their original size.

The present invention overcomes some of the disadvantages found with time-consuming processes of electroplating and etching. Some of these prior art methods are not only timeconsuming and hence costly but they oftentimes result in the loss of an aperture mask because of improper etching or electroplating of the mask. The present invention overcomes these disadvantages by providing annular members that can be placed in the apertures to reduce the diameter of the openings. Another advantage of the present method is that because the mask does not have to be subjected to chemical baths and treatments there is less chance of contaminating the aperture.

BRIEF SUMMARY OF THE INVENTION Briefly, the present invention comprises placing a set of annular members having an outer diameter which is slightly less than the openings of the largest diameter of the aperture mask on top of the aperture mask. By vibrating or shaking the mask the annular members fall into the larger holes or apertures on the shadow mask. As the central opening of the annular member has been prepared with a suitable size opening for laying a phosphorus dot pattern the mask with the annular members in the apertures can now be used to lay a phosphorus dot pattern.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross sectional view showing an aperture mask having annular members located therein;

FIG. 2 shows one type annular member having a straight outside wall;

FIG. 3 shows an annular member having a beveled outside wall;

FIG. 4 shows an annular member having a curved outside wall;

FIG. 5 shows an annular member having a slanted outside wall;

FIG. 6 shows apparatus for placing the annular members in the holes of the aperture mask;

FIG. 7 is a cross sectional view showing an aperture mask having the annular members shown in FIG. 4 located therein;

FIG. 8 shows a greatly enlarged view of an aperture and an annular member and the relative dimensions of the aperture and the annular members.

FIG. 9 shows light being projected through an annular member and onto a phosphorus screen.

DESCRIPTION or THE PREFERRED EMBODIMENT Referring to the drawings, FIG. 1 shows in cross section a portion of an aperture mask 10 having a plurality of apertures 12 located therein. Apertures 12 have a cone-shaped wall 13 that slopes inward to a minimum diameter opening D from one side of the mask 10 and another cone-shaped wall 13a that slopes inward to the smallest diameter opening D of the aperture from the opposite side of mask 10. Located within apertures 12 are annular or ringlike members 15 which have a central opening designated by D With annular members 15 positioned within apertures of mask 10 it reduces the opening through apertures 12 just as if apertures had been reduced through electroplating or the like.

FIG. 2 through 5 show various preferred shapes of annular members 15 that are suitable for placing in apertures 12 of mask 10.

More specifically, FIG. 2 shows an annular member 20 having a straight outer wall section 20a and FIG. 3 shows a similar annular member 21 having a V-shaped outer wall section 210.

FIG. 4 shows an annular member 23 having a curved outer wall 23a, and FIG. 5 shows an annular member 24 having a beveled outer wall 24a for forming mating engagement with the angled walls of aperture 12.

The various cores or annular members shown in FIGS. 2-5 can be made in any one of a number of methods such as etching or molding. Likewise, the various materials that can be used in the manufacture of a set of annular members can vary although in some instances magnetic substances such as ferrite cores are preferred as an operator can hold the cores on the mask by applying a suitable magnetic field.

FIG. 6 shows an apparatus for placing the annular members in the apertures of the mask 10. In a typical shadow mask, there may be over 440,000 apertures in the aperture mask. Obviously, if each of these apertures are to receive an annular member there must be some apparatus for quickly placing the tiny annular members in the apertures of the face mask. Referring to FIG. 6, reference numeral 30 designates such as apparatus for quickly placing the annular members in the aperture of the mask. Apparatus 30 comprises a shaker table 31 that is driven by a shaker mechanism 32. Shaker table 31 has a preformed or dome-shaped mask 10 located thereon. The edges 10a of the mask are in sealed contact with table 31. Located within table 31 is a vacuum chamber 33 that is connected to a vacuum source 34 for producing a lower pressure on the under side of the mask than on the topside of the mask. Located around the top of the mask is a retaining flange 38 that prevents the annular members from being shaken off the face of the mask. Flange 38 is not an integral part of the mask but is merely placed on top of the mask to prevent loss of the annular members.

In operation, shaker mechanism 32 drives the shaker table 3! and mask 31 in a vibrating motion. At the same time, vacuum pump 34 draws air from chamber 33 thus creating a low pressure region on the bottom side of mask 10. As mask is vibrated back and forth, tiny annular members 40 are dispersed onto the mask from container 41. The shaking action of the mask causes the annular member 40 to fall into the apertures. Once an annular member falls into the aperture the pressure differential produced by the lower pressure on the underside of the mask causes the annular members to be firmly held in the apertures even though the table continues to vibrate.

FIG. 7 shows a mask 10 having annular members 23 which were shown in FIG. 4, located therein. Located on top of mask 10 is a thin layer of transparent material 40 that acts as a restraining barrier to hold the annular members within the apertures of the mask after the vacuum source has been shut off. With material 40 over the mask, the mask can be moved or manipulated without the annular members falling out of the apertures.

FIG. 8 shows in enlarged form annular member 23 and an aperture 12. The largest dimension of aperture 12 is designated by D and the smallest dimension of aperture 12 is designated by D Similarly the largest dimension of annular member 23 designated by D and the central opening of the annular core member is designated by D The thickness of the aperture mask is designated by T. A typical set of dimensions are as follows; however, no limitation is intended thereto:

D 0.021 inches D 0.016 inches D 0.018 inches D 0.010 inches T 0.008 inches In order to obtain a good seating of the annular core member within the aperture as well as effectively reducing the diameter of the opening for light to pass through it, it has been found desirable to have D D D D With these relative dimensions the annular members will seat in axial alignment with the apertures of the mask.

FIG. 9 shows in schematic form the operation of printing the phosphorus dot pattern using annular member 23 in the aperture 12 of the shadow mask. A suitable light source 45 directs light through the central opening D of annular member 23 and onto phosphoric screen 46 that is located on the back of face plate 47 of the TV picture tube. After suitable developing, a phosphorus dot of diameter D. is produced on back of face plate 47. After the primary dots are formed in this manner, the annular members are removed and reused to print another pattern on'another mask. Also, this mask can now be permanently attached to the inside of the television tube without altering the physical characteristics of the tube.-

We claim:

1. in combination a mask useable in a color TV picture tube for laying down a pattern of colored phosphorus dots on the face plate of the tube and for later functioning as an aperture mask during normal operation of the picture tube comprising: a preformed mask having a plurality of openings arranged in predetermined pattern; a plurality of members located in a nesting relationship in said openings; each of said members having an opening of predetermined size suitable for laying down a phosphorus dot pattern on said face plate.

2. The invention as described in claim 1 wherein said members comprise annular members.

3. The invention as described in claim 2 wherein said annular members have a circularcentral openings. I

4. The invention as described in claim 1 wherein said members have an outside configuration for forming mating engagement with the openings in said aperture mask.

5. The invention of claim 4 wherein the sidewalls of the apertures and at least a portion of the sidewalls of said annular members are beveled to form mating engagement with one another.

6. The invention of claim 4 including means for holding said annular members in said apertures.

7. A TV shadow mask for use in laying down a phosphorus dot pattern comprising:

a sheet of metallic material having a plurality of coneshaped openings which are spaced in a predetermined pattern; said cone-shaped opening having a maximum diameter D and a minimum diameter D a plurality of nesting members having an outside diameter D and a central diameter D., with D, D D D., to thereby provide a nesting member for supporting itself within said aperture while reducing the diameter of the opening of said apertures to enable the mask to be used to lay down a phosphorus dot pattern. 

1. In combination a mask useable in a color TV picture tube for laying down a pattern of colored phosphorus dots on the face plate of the tube and for later functioning as an aperture mask during normal operation of the picture tube comprising: a preformed mask having a plurality of openings arranged in predetermined pattern; a plurality of members located in A nesting relationship in said openings; each of said members having an opening of predetermined size suitable for laying down a phosphorus dot pattern on said face plate.
 2. The invention as described in claim 1 wherein said members comprise annular members.
 3. The invention as described in claim 2 wherein said annular members have a circular central openings.
 4. The invention as described in claim 1 wherein said members have an outside configuration for forming mating engagement with the openings in said aperture mask.
 5. The invention of claim 4 wherein the sidewalls of the apertures and at least a portion of the sidewalls of said annular members are beveled to form mating engagement with one another.
 6. The invention of claim 4 including means for holding said annular members in said apertures.
 7. A TV shadow mask for use in laying down a phosphorus dot pattern comprising: a sheet of metallic material having a plurality of cone-shaped openings which are spaced in a predetermined pattern; said cone-shaped opening having a maximum diameter D1 and a minimum diameter D2; a plurality of nesting members having an outside diameter D3 and a central diameter D4 with D1>D3>D2>D4 to thereby provide a nesting member for supporting itself within said aperture while reducing the diameter of the opening of said apertures to enable the mask to be used to lay down a phosphorus dot pattern. 